What is a Class A subnet?

Answer

A class A subnet uses the first octet of an IP address to designate the network ID, and the remaining three octets for the designation of the Host ID.

Host ID
|  |  |
|  |  |
ip address      xxx.xxx.xxx.xxx
|
|
Network ID

The first bit of the first octet is always set to zero to indicate a Class A address, therefore this leaves 7 bits to represent the Network ID. This means that there is a maximum of 127 Class A addresses and because 127 is reserved for the loopback function of the network card this gives a maximum of 126 Class A addresses.

As the remaining 24 bits are available for the Host ID this provides for 16, 777,214 or (2²⁴) ?2 hosts per network.

Gordano software assumes that you are using a Class C subnet mask for local mail authentication. If you are using a Class A subnet, you will need to alter the local IP settings appropriately.

Keywords:IP Address subnet class